As an end effector to be used for achieving various operations in a robot arm, a hand, which is capable of holding an object or the like serving as a work subject, has been utilized. The hand, which is attached to the tip of a robot arm, needs to have a small size and light weight so as to make the load of the robot arm as small as possible.
In order to satisfy these demands, in the conventional art, a light-weight hand having a simple structure has been proposed in which, as shown in FIG. 11, two movable fingers 101A and 103, fixed pulleys 120, 121 and a movable pulley 141, which are rotatably secured to joint shafts 108 and 111, and a wire 125, secured to the two movable fingers 101A and 103 through the fixed pulleys 120 and 121 and the movable pulley 141, are provided so that, by driving the movable pulley 141 to make a translation movement, the wire 125 is pulled so that each of the fingers 101A and 103 is driven to carry out an opening/closing movement (see JP-B No. 5-196).